Liquid-crystal modulator array

Abstract

A liquid-crystal phase modulator array, comprising a planar electrode on one glass support and an array of finger electrodes on the other glass support with a nematic liquid filling the gap between the two supports. The alignment layer between the finger electrodes and the liquid crystal is rubbed to have an alignment direction extending along the finger electrodes and prependicular to the gap between them. The alignment layer between the planar electrode and the liquid crystal is rubbed in the anti-parallel direction. Voltages are selectively applied to different ones of the finger electrodes to provide a phase modulator array for light passing through the assembly. The alignment direction of the invention eliminates ragged edges adjacent the edges of the finger electrodes arising from an instability. Thereby, the finger electrodes can be made much narrower, and more pixels can be included in the array. The phase modulator of the invention can be advantageously used in a Fourier optical pulse shaper.

What is claimed is: 
     
       1. A liquid-crystal modulator array, comprising: a first support having formed thereon an array of electrodes extending in parallel in a first electrode direction and having respective lengths, widths, and ratios of said respective lengths to said respective widths of at least 10;   a second support separated from said first support by a cell gap and having formed thereon a common electrode facing all of said array of electrodes along their said respective widths;   a first alignment layer disposed on said first support on its side facing said cell gap and having a first alignment direction parallel to said first electrode direction; and   a liquid crystal filling said cell gap and being at least partially aligned by said first alignment layer.   
     
     
       2. A liquid-crystal modulator array as recited in claim 1, further comprising a second alignment layer disposed on said second support on its side facing said cell gap and having a second alignment direction substantially parallel or anti-parallel to said first alignment direction, said liquid crystal being partially aligned by said second alignment layer. 
     
     
       3. A liquid-crystal modulator array as recited in claim 2, wherein said liquid crystal is a nematic liquid crystal. 
     
     
       4. A liquid-crystal modulator array as recited in claim 3, wherein electrodes in said array have widths perpendicular to said first direction of less than 50 μm. 
     
     
       5. A liquid-crystal modulator array system including the liquid-crystal modulator array recited in claim 2, wherein said supports, electrodes, alignment layers, and liquid crystal form a phase modulator array and further comprising: an amplitude modulator array; and   an optical system focusing input light at a first one of said phase and amplitude modulator arrays and focusing light passing through said first one modulator array at a second one of said phase and amplitude modulator arrays.   
     
     
       6. A liquid-crystal phase modulator array, comprising: a first transparent support;   a plurality of parallel electrodes formed on said first support and extending along a first electrode direction and having electrode gaps formed between neighboring ones of said parallel electrodes;   a first alignment layer formed over said parallel electrodes and having an alignment direction parallel to said first electrode direction;   a second transparent support;   a common electrode formed on said second support;   a second alignment layer formed over said common electrode and having an alignment direction anti-parallel to said first electrode direction, said first and second alignment layers being separated by a cell gap; and   a liquid crystal filling said cell gap and being aligned adjacent to boundaries of said cell gap by said first and second alignment layers.   
     
     
       7. A phase modulator array as recited in claim 6, wherein said liquid crystal comprises a nematic liquid crystal. 
     
     
       8. A phase modulator array as recited in claim 7, wherein said parallel electrodes have widths perpendicular to said first electrode direction of less than 50 μm. 
     
     
       9. A phase modulator array as recited in claim 8, wherein said parallel electrodes have a length-to-width ratio of at least 10. 
     
     
       10. A phase modulator array as recited in claim 9, wherein said electrode gaps have widths of no more than 2.5 μm. 
     
     
       11. A Fourier pulse shaper, comprising: a liquid-crystal modulator array comprising a first support having formed thereon an array of electrodes extending in parallel in a first electrode direction, a second support separated from said first support by a cell gap and having formed thereon at least one electrode, a first alignment layer disposed on said first support on its side facing said cell gap and having a first alignment direction parallel to said first electrode direction, a second alignment layer disposed on said second support on its side facing said cell gap and having a second alignment direction substantially parallel or anti-parallel to said first alignment direction, and a liquid crystal filling said cell gap and being at least partially aligned by said first and said second alignment layers;   first energy dispersive means for spatially separating frequency components of an input beam into a frequency-dispersed beam impinging said liquid-crystal modulator array, said different frequency components impinging portions of said modulator array corresponding to different ones of said array of electrodes; and   second energy dispersive means for recombining portions of said frequency components passing through said modulator array into an output beam.   
     
     
       12. A Fourier pulse shaper as recited in claim 11, wherein said first and second energy dispersive means comprise diffraction gratings and further comprising polarization rotating means interposed between each of said gratings and said modulator array. 
     
     
       13. A Fourier pulse shaper as recited in claim 11, wherein the liquid-crystal modulator array is a phase modulator array and further comprising: an amplitude modulator array; and   an optical system focusing said frequency-dispersed beam at a first one of said phase and amplitude modulator arrays and focusing light passing through said first one modulator array at a second one of said phase and amplitude modulator arrays.